Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$112.27	13.749%	$127.706	$127.71	$127.70	$127.70
Purchase #2	$78.38	5.757%	$82.8923	$82.89	$82.90	$82.90
Purchase #3	$214.51	12.612%	$241.564	$241.56	$241.55	$241.60
Purchase #4	$74.44	4.436%	$77.7422	$77.74	$77.75	$77.70
Purchase #5	$244.48	7.247%	$262.1975	$262.20	$262.20	$262.20
Purchase #6	$108.29	6.864%	$115.723	$115.72	$115.70	$115.70
Purchase #7	$63.85	10.604%	$70.6207	$70.62	$70.60	$70.60
7 purchase totals =	$896.22		$978.4457	$978.44	$978.40	$978.40